Brake squeal

[nuron]

My brakes are making a squealing noise whenever I come to a stop--not at the initial application of the brakes but just when the car comes to about 5MPH. I checked the pads and they had plenty of life left, so I sprayed some brake quiet stuff on the pads anyway. After that, the noise was still there but went away after some hard stops. When my brother drove it again, the noise came back. Would this be from the material of the pads? I'm curious why this didn't happen before...Although, I'm used to the pads squealing all the way from coming to a stop, not just in the last 5MPH.

[fishexpo101]

Could be some contamination on the pad material or on the rotor itself. Noise comes from vibrations transmitted from the pad to the caliper and/or rotor (pad actually vibrates, which causes the squealing noise) - probably from grease that has dried off the shims on the back of the pads. Might need something a little heavier to help dampen that vibration.

Choice of pad material or when the pad gets overheated - could cause squealing later. Some higher performance pads do that too - maybe an initial chirp with application, to smooth quiet operation until the last couple of MPH - then they squeal.

Make sure your brother isn't riding the brakes - could have cooked off the brake quiet material or cooking up the pads. Make sure the caliper is not locked up or sticking on you - normally can tell by comparing the inside and outside pad thicknesses. Sliding caliper design will tend to eat the inside pad a little faster - but should not be a significant difference (i.e, the inside pad is half the thickness of the outside pad - or worn to a wedge, where the trailing or leading edge is significantly thinner than the other side.)

Sometimes you have to clean off the rotors (could get away with some light scuffing with an emery paper or may need to turn down the rotor a hair), to help remove the old friction transfer layer and re-bed the rotors/pads.